WO2015004755A1

WO2015004755A1 - Optical film thickness measurement device, thin film forming device, and method for measuring film thickness

Info

Publication number: WO2015004755A1
Application number: PCT/JP2013/068887
Authority: WO
Inventors: 旭陽佐井; 陽平日向; 芳幸大瀧
Original assignee: 株式会社シンクロン
Priority date: 2013-07-10
Filing date: 2013-07-10
Publication date: 2015-01-15
Also published as: JPWO2015004755A1

Abstract

　Provided is a reflective optical-film-thickness-measurement device attached to a substrate holder of a rotary optical-thin-film-forming device, the optical-film-thickness-measurement device measuring the thickness of the optical thin film on a rotating substrate and not being readily affected by variation in angle of the rotating substrate. The present invention is provided with: a projection-side lens unit provided with a projection part (43) for projecting measurement light towards a rotating substrate (S), and projection-side lenses (51, 56) disposed between the substrate (S) and the projection part (43), the projection side lenses (51, 56) receiving the measurement light emitted from the projection part (43) and guiding the measurement light to the substrate (S); and a reception-side lens unit provided with a light reception part (44) for receiving light reflected by the substrate (S) from the measurement light, and reception-side lenses (52, 57) disposed between the substrate (S) and the reception part (44), the reception side lenses (52, 57) receiving the light reflected by the substrate (S) and guiding this reflected light to the reception unit (44). At least some of the optical path of the reception-side lens unit and the optical path of the projection-side lens unit are separate, and the active area of the projection-side lens unit is less than the active area of the reception-side lens unit.

Description

Optical film thickness meter, thin film forming apparatus, and film thickness measuring method

The present invention relates to an optical film thickness meter, a thin film forming apparatus, and a film thickness measuring method for measuring the film thickness of an optical thin film formed on a substrate.

An optical thin film is formed on the substrate surface by physical vapor deposition such as sputtering to produce optical products such as interference filters, such as antireflection filters, half mirrors, various bandpass filters, dichroic filters, and coloring on the surface of various decorative products. In general, it is common to manufacture decorative articles having specific optical characteristics by coating.
Among them, the application of physical vapor deposition such as sputtering to precision optical products such as wide-angle lenses used in single-lens reflex digital cameras and projectors and precision optical filters for game machines is spreading.
As a method of measuring the film thickness of a thin film formed on a substrate, a method using a crystal film thickness meter, or an indirect optical film that monitors a film thickness using a monitor substrate arranged at a position different from the film formation substrate There is a thickness monitor method.
However, precise film thickness measurement is difficult with a quartz film thickness meter or an indirect optical film thickness monitor system.

The indirect optical film thickness monitoring method is so-called indirect measurement, and there is a distance between the monitor substrate and the film formation substrate, and a physical space is separated. In addition, in the electron beam heating vapor deposition system, there are unstable factors such as changes in the distribution of vapor deposition particles after electron beam irradiation and the influence of gas released from the wall surface of the vacuum system, and the density of the film material scattered in the vacuum system. Is not constant, and there is a scattering distribution of the film substance in the vacuum apparatus. Therefore, the film thickness to be formed varies depending on the position of the substrate disposed in the vacuum apparatus, and is not suitable for highly accurate film formation.
Therefore, when a thin film of precision optical parts is formed by physical vapor deposition, the film thickness accuracy required for precision optical parts is achieved even if the film thickness is controlled by a quartz film thickness meter or an indirect optical film thickness monitor method. This is difficult and causes a decrease in the production yield of precision optical components.
In the indirect type optical film thickness monitoring method, an error due to a physical space between the monitor glass and the film formation substrate is currently corrected with a parameter called tooling.
Therefore, in recent years, measurement and monitoring of film thickness by a direct-viewing optical film thickness monitor method that directly measures the film thickness of a substrate whose optical characteristics are to be measured has come into practical use. The direct-view type optical film thickness monitor method is widely used when a film is formed on a stationary substrate by a vacuum deposition method, a sputtering method, or the like.

On the other hand, as an apparatus for mass production of optical filters by forming a film on a large number of substrates, a carousel type substrate holder in which a plurality of substrates are held on the outer peripheral surface of a rotating drum, a dome type rotating substrate holder, etc. A film forming apparatus is known.
A carousel type or dome type rotary substrate holder rotates around a rotation axis while holding a plurality of substrates. The substrate revolves around the rotation axis, and there is no substrate that remains in one place while the substrate holder is rotating.
Therefore, in order to measure a physical property value such as a film thickness by the direct-view type optical film thickness monitor method, it is necessary to temporarily stop the rotation of the substrate holder and then perform an optical measurement or the like on the substrate. In such a measuring method, the thin film forming process must be stopped every time the film thickness is measured, and thus the thin film forming process takes time.

Therefore, the inventors of the present invention have used a direct-view optical film thickness monitor method to measure and monitor the film thickness in a film deposition apparatus equipped with a carousel-type substrate holder. There has been proposed one that uses a reflection-type optical film thickness meter that projects light and calculates the film thickness by receiving and analyzing the reflected light (for example, Patent Document 1).

Patent No. 4800734 (paragraphs 0092 to 0124, FIGS. 1, 2 and 6)

The film thickness meter of Patent Document 1 is provided on the wall of a vacuum chamber of a carousel-type sputtering apparatus, and includes a light source, a light projecting optical fiber, a light projecting photometric probe, a condensing lens, and a light receiving device. A photometric probe, a light receiving optical fiber, and an optical measuring means. In the film thickness meter, a photometric probe for light projection and light reception is opposed to a substrate held on the outer peripheral surface of a rotary drum type substrate holder.
In film thickness measurement using the film thickness meter of Patent Document 1, light from a light source is projected from an optical fiber, and is projected onto a rotating substrate through a light metering probe and a condenser lens. The reflected light partially transmitted and reflected at the interface between the substrate surface and the deposited thin film is received by the optical fiber through the condensing lens and the photometric probe for light reception and guided to the optical measuring means. The intensity of light is measured by an optical measuring means.
According to the film thickness meter of Patent Document 1, even in a carousel type thin film forming apparatus in which a rotating drum type substrate holder rotates at a high speed, a direct view of directly measuring the thickness of a thin film on a sample substrate without providing a monitor substrate is provided. The film thickness could be measured by the mold method.

However, since the film thickness meter of Patent Document 1 measures the film thickness of the thin film on the substrate attached to the side surface of the substrate holder that rotates at high speed, photometry for light projection and light reception during film formation. The emission angle and incident angle of light onto the substrate surface by the probe are constantly changing.
Therefore, it is difficult to control the emission angle and incidence angle of light on the substrate surface.If the substrate is inclined due to mounting error or rotation unevenness and the incident angle of the measurement light exceeds a certain angle, the reflected light is reflected from the condenser lens. It sometimes protrudes to the outside, making measurement difficult.

The present invention has been made in view of the above circumstances, and its purpose is to directly measure the thickness of an optical thin film on a rotating substrate attached to a substrate holder of a rotating optical thin film forming apparatus. A reflective optical film thickness meter, a thin film forming apparatus, and a film thickness measuring method, which are less affected by variations in the angle of a rotating substrate and have high measurement accuracy, a thin film forming apparatus, and a film It is to provide a thickness measuring method.

According to the optical film thickness meter of the first aspect, the object is to attach the optical thin film on the substrate which is attached to the substrate holder of the rotary optical thin film forming apparatus and rotates according to the rotation of the substrate holder. A reflection-type optical film thickness meter for measuring a film thickness, wherein a measurement light is projected toward the rotating substrate, and is disposed between the light projection unit and the substrate. A projection-side lens unit comprising a projection-side lens that receives the measurement light emitted from the light projecting unit and guides the measurement light to the substrate, and the reflected light of the measurement light from the substrate. A light receiving side lens, and a light receiving side lens that is disposed between the light receiving unit and the substrate, receives light reflected from the substrate, and guides the reflected light to the light receiving unit. A light path of the light receiving side lens unit and light of the light projecting side lens unit. And it is at least partially separated, the effective area of the light projection-side lens unit is solved by a small fact, than the effective area of the light receiving side lens unit.

As described above, since the effective area of the light emitting side lens unit is smaller than the effective area of the light receiving side lens unit, the rotating measurement target substrate is measured by the substrate mounting error, the rotation unevenness of the substrate holder, etc. Even when tilted with respect to a plane perpendicular to the light axis, the reflected light reflected by the substrate is unlikely to deviate from the optical path of the light-receiving lens, and the amount of reflected light can be accurately detected. As a result, it is possible to accurately and stably measure the film thickness of the optical thin film formed on the rotating substrate while minimizing the light intensity noise due to the effects of substrate mounting errors and uneven rotation of the substrate holder. It becomes possible. As a result, the process of repeating the correction of the film thickness after the film formation becomes unnecessary.

In addition, since it can be applied to a thin film on a rotating substrate, it can be applied to a thin film forming apparatus equipped with a drum-type or dome-type rotary substrate holder, and forms a thin film on a large number of substrates in a short time. It is possible to provide an optical film thickness meter suitable for a mass production type thin film forming apparatus.
In addition, since it has a light projecting unit that projects measurement light toward the rotating substrate, the film thickness of the thin film on the sample substrate is directly measured without providing a separate monitor substrate in a rotating optical thin film forming apparatus. A direct-view optical film thickness meter can be provided. Therefore, when a mass-produced rotary optical thin film forming device is used, unlike a quartz oscillator thickness meter or an indirect type optical film thickness meter, it has a high accuracy as required for precision optical components. The film thickness can be controlled.

The light-projecting side lens and the light-receiving side lens are separate and independent lenses, and the effective diameter of the light-projecting side lens is preferably smaller than the effective diameter of the light-receiving side lens. is there.
As described above, since the lens on the light projecting side and the lens on the light receiving side are separate lenses independent from each other, the optical paths of the measurement light and the reflected light can be separated into two with a simple configuration. .
In addition, since the effective diameter of the lens on the light emitting side is smaller than the effective diameter of the lens on the light receiving side, even when the substrate is tilted when measuring the film thickness, the light receiving having a larger effective diameter than the lens on the light projecting side is received. The lens on the side can receive the reflected light.

The angle between the optical axis of the light-projecting lens and the optical axis of the light-receiving lens is 3 ° to 10 °, and the distance from the light-projecting lens to the substrate is: The distance from the light projecting unit to the lens on the light projecting side may be longer, and the distance from the lens on the light receiving side to the substrate may be longer than the distance from the light receiving unit to the lens on the light receiving side.
Thus, by increasing the distance from the lens on the light emitting side to the substrate and the distance from the lens on the light receiving side to the substrate, the light incident on the substrate is made closer to parallel light, and the film thickness measurement accuracy is improved. It becomes possible to improve further.

The angle formed between the optical axis of the light-projecting lens and the optical axis of the light-receiving lens passes through the intersection of the optical axis of the light-projecting lens and the optical axis of the light-receiving lens. The lens on the light receiving side may be arranged at a position where the straight line passes.
With this configuration, the light-receiving side lens and the light-projecting side lens can be arranged close to each other. As a result, the lens on the light-projecting side and the lens on the light-receiving side can be made up of lenses with a larger effective diameter while being compactly arranged in a narrow area, and the film thickness can be measured with high accuracy. An optical film thickness meter suitable for measuring the film thickness of an optical thin film for precision optical components can be realized.

In addition, between the lens on the light projecting side and the lens on the light receiving side, and the substrate to be measured, the lens on the light projecting side, the lens on the light receiving side, and a condensing lens facing the substrate, The effective diameter of the condensing lens may be larger than the sum of the effective diameter of the light-projecting side lens and the effective diameter of the light-receiving side lens.
As described above, since the light-projecting lens, the light-receiving lens, and the measurement target substrate are provided with the light-projecting lens, the light-receiving lens, and the condensing lens facing the substrate, the substrate It is possible to make the light incident on the light beam closer to parallel light, and to improve the accuracy of film thickness measurement. As a result, the film thickness can be measured with high accuracy, and an optical film thickness meter suitable for measuring the film thickness of the optical thin film for precision optical components can be realized.
Further, by further providing a condensing lens as described above, the optical film thickness meter can be configured compactly while keeping the incident angle of the measurement light small and improving the parallelism of the incident light.

In addition, the light projecting side lens and the light receiving side lens are formed as a single light projecting / receiving side combined lens, and the measurement light is interposed between the light projecting / receiving side lens and the light receiving unit. A beam splitter may be disposed that reflects the reflected light at the same time as passing through and has a beam branching surface inclined with respect to the axis of the reflected light.

Since it is configured in this manner, at least a part of the optical path of the projected measurement light and the reflected light to be received can be obtained without configuring the light-projecting lens and the light-receiving lens as separate bodies. Can be separated.
Even when the substrate to be measured is tilted with respect to a plane perpendicular to the axis of the measurement light due to substrate mounting error, rotation unevenness of the substrate holder, etc., the reflected light reflected by the substrate is projected. It becomes difficult to deviate from the optical path of the light-receiving side combined lens, and the amount of reflected light can be accurately detected. As a result, it is possible to accurately and stably measure the film thickness of the optical thin film formed on the rotating substrate while minimizing the light intensity noise due to the effects of substrate mounting errors and uneven rotation of the substrate holder. It becomes possible. As a result, the process of repeating the correction of the film thickness after the film formation becomes unnecessary.

An aperture for limiting the amount of measurement light emitted from the light projecting unit is provided between the light projecting and receiving side combined lens and the light projecting unit, and the light projecting side lens unit is provided on the light projecting and receiving side. You may comprise from a combined lens, the said beam splitter, and the said aperture.
With this configuration, it is possible to make the effective area of the measurement light beam smaller than the effective area of the reflected light beam, mounting errors of the substrate, uneven rotation when the substrate holder is a rotary type, etc. Therefore, even when the rotating substrate to be measured is tilted with respect to the plane perpendicular to the axis of the measurement light, the reflected light is difficult to deviate from the optical path of the lens for the light projecting and receiving side, and the amount of the reflected light Can be detected accurately. As a result, it is possible to accurately and stably measure the film thickness of the optical thin film formed on the rotating substrate while minimizing the light intensity noise due to the effects of substrate mounting errors and uneven rotation of the substrate holder. It becomes possible. As a result, the process of repeating the correction of the film thickness after the film formation becomes unnecessary.

The lens may be a combined lens in which a plurality of lenses are combined so as to remove aberration of a beam of light emitted from the lens.
Since it is configured in this way, it is possible to prevent aberrations such as chromatic aberration and spherical aberration from occurring in the light beam emitted from the light projecting side lens, the light receiving side lens, the light projecting / receiving side lens or the condenser lens, The film thickness of the optical thin film can be measured more accurately.

According to the thin film forming apparatus of the ninth aspect, the subject is a substrate holder that can rotate while supporting a substrate in a vacuum vessel, and a thin film disposed opposite to the substrate held by the substrate holder. Forming means, and an optical film thickness meter that measures the film thickness of the optical thin film on the substrate by irradiating the substrate with measurement light while the substrate holder to which the substrate is attached is rotating. A thin film forming apparatus provided, wherein the optical film thickness meter comprises the optical film thickness meter according to any one of claims 1 to 8.

With this configuration, in a thin film forming apparatus equipped with a rotary substrate holder, the substrate holder is hardly affected by variations in the substrate tilt angle due to substrate mounting errors, substrate holder rotation unevenness, etc. Accordingly, the thickness of the optical thin film on the rotating substrate can be measured accurately and stably.

According to the film thickness measuring method according to claim 10, the object is a reflective method for measuring the film thickness of an optical thin film formed on a rotating substrate according to the rotation of the substrate holder of the rotary optical thin film forming apparatus. The method of measuring a film thickness of the method, wherein the measurement light is projected from the light projecting unit toward the rotating substrate through a light projecting side lens unit including a lens on the light projecting side. The reflected light of the measurement light is provided with a light-receiving side lens having an effective area larger than the effective area of the light-projecting side lens unit, and at least a part is separated from the optical path of the light-projecting side lens unit The light quantity of the reflected light that is guided to the light receiving unit through the light receiving side lens unit having an effective area larger than the effective area of the light projecting side lens unit and received by the light receiving unit By analyzing the data, the optical Measuring the thickness of a film, it is solved by.

Even if the substrate to be measured is tilted with respect to the plane perpendicular to the axis of the measurement light due to the mounting error of the substrate, the rotation unevenness of the substrate holder, etc. The reflected light reflected by the substrate is unlikely to deviate from the optical path of the lens on the light receiving side, and the amount of reflected light can be accurately detected. As a result, it is possible to accurately and stably measure the film thickness of the optical thin film formed on the rotating substrate while minimizing the light intensity noise due to the effects of substrate mounting errors and uneven rotation of the substrate holder. It becomes possible. As a result, the process of repeating the correction of the film thickness after the film formation becomes unnecessary.

In addition, since it can be applied to a thin film on a rotating substrate, it can be applied to a thin film forming apparatus equipped with a drum-type or dome-type rotary substrate holder, and forms a thin film on a large number of substrates in a short time. Even in a mass production type thin film forming apparatus, the film thickness of an optical thin film can be measured accurately and stably.

According to the present invention, since the effective area of the light-projecting side lens unit is smaller than the effective area of the light-receiving side lens unit, the rotating measurement target substrate is caused by the substrate mounting error, the rotation unevenness of the substrate holder, and the like. Even when tilted with respect to a plane perpendicular to the axis of the measurement light, the reflected light reflected by the substrate is unlikely to deviate from the optical path of the lens on the light receiving side, and the amount of reflected light can be detected accurately. As a result, it is possible to accurately and stably measure the film thickness of the optical thin film formed on the rotating substrate while minimizing the light intensity noise due to the effects of substrate mounting errors and uneven rotation of the substrate holder. It becomes possible. As a result, the process of repeating the correction of the film thickness after the film formation becomes unnecessary.

It is the fragmentary sectional view which looked at the thin film forming apparatus concerning one embodiment of the present invention from the upper surface. It is a functional block diagram which shows the structure of the optical film thickness meter which concerns on one Embodiment of this invention. It is a schematic explanatory drawing which shows lens arrangement | positioning of the optical film thickness meter which concerns on one Embodiment of this invention. It is a schematic explanatory drawing which shows the lens unit arrangement | positioning of the optical film thickness meter which concerns on other embodiment of this invention. It is a schematic explanatory drawing which shows the lens arrangement | positioning of the optical film thickness meter which concerns on other embodiment of this invention. FIG. 6 is a perspective explanatory view of lens arrangement of the optical film thickness meter of FIG. 5. Examples 1 and 2, using an optical film thickness meter having a lens arrangement according to Comparative Example 1, when measuring light is emitted from a substrate having an inclination angle of 0.0 to 2.0 ° from the substrate It is a graph which shows the result of having calculated the relative reflectance of the reflected light. FIG. 3 shows the result of examining the variation in light quantity during thin film formation when the experiment of forming a multilayer AR film on the substrate S is repeated a plurality of times by controlling the film thickness with a film thickness meter having the lens arrangement of FIG. It is a graph to show. FIG. 3 shows the result of examining the dispersion of the spectral characteristics of the multilayer AR film when the experiment of forming the multilayer AR film on the substrate S is repeated a plurality of times by controlling the film thickness with the film thickness meter having the lens arrangement of FIG. It is a graph to show.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that members, arrangements, and the like described below do not limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.
A thin film forming apparatus in which a film thickness meter 40 as an optical film thickness meter of the present embodiment is used includes a rotary substrate holder that rotates a substrate holder that holds a substrate.
For example, the substrate holding surface of the substrate holder and the normal of the substrate held on the substrate holding surface with respect to the rotation axis of the substrate holder, such as a dome-shaped substrate holder, a carousel type substrate holder with a rotating drum, etc. It is particularly preferably used for those in which the slope is inclined.
In general, in a dome-shaped or drum-type substrate holder, the angle between the measurement light emitted to the substrate and the substrate surface changes according to the rotation of the substrate holder. It is difficult to keep the film thickness measurement accuracy high. On the other hand, in the optical film thickness meter of the present embodiment, the film thickness of the optical thin film on the substrate rotating with the substrate holder can be accurately and stably hardly affected by variations in the substrate tilt angle. It can be measured.
However, the substrate holder is not limited to a dome type formed in a spherical shape or a cylindrical shape, but includes a polygonal pyramid shape or a polygonal column shape.
The optical film thickness meter according to the present invention is not limited to a thin film forming apparatus having a rotary substrate holder that revolves around the substrate, but also used in an in-line thin film forming apparatus in which the substrate moves in a linear direction. Can do.

(Sputtering device 1)
An example in which the film thickness meter 40 of this embodiment is used in the carousel type sputtering apparatus 1 will be described. Of course, the present invention is not limited to the sputtering apparatus, and may be used for other thin film forming apparatuses such as a vacuum deposition apparatus and a CVD apparatus.
A sputtering apparatus 1 in which the film thickness meter 40 of the present embodiment is installed is shown in FIG.
1 includes a vacuum vessel 11, a rotating drum 12, a pair of

sputtering sources

20A and 20B, and a plasma source 30 as main components.
The vacuum vessel 11 is a known rectangular vacuum vessel used in sputtering, and is divided into a thin film forming chamber 11A and a load lock chamber 11B by a door.
The rotating drum 12 is a substrate holder that holds the substrate S, and has a substantially cylindrical shape with a vertical rotation axis Z as the center, as shown in FIG. 1, and is configured to hold the substrate S on the outer peripheral surface. Yes. The rotating drum 12 only needs to be rotatable about the rotation axis Z, and may be formed of a polygonal column or a conical hollow body.

A disc-shaped frame (not shown) is fixed to the lower end of the rotating drum 12 so as to close a hollow space in the rotating drum 12, and a rotating shaft of a motor (not shown) is connected to the center of the frame. ing. The rotary drum 12 can be driven to rotate by driving a motor (not shown).
Further, as shown in FIG. 2, a timing detection reflecting plate 15 is attached to the upper end portion of the rotating drum 12, and the passage thereof can be detected by the timing sensor 16.
The

sputtering sources

20A and 20B are means for depositing a metal or an incomplete compound thereof on the substrate S. The

sputtering sources

20A and 20B are each a known dual cathode type magnetron sputtering source, and a pair of targets are formed on the side walls of the thin film forming chamber 11A. 22A and 22B are provided to face the substrate S.
As shown in FIG. 1, the

sputtering sources

20A and 20B include a pair of

magnetron sputtering electrodes

21A and 21B that hold a pair of

targets

22A and 22B, respectively, and an AC power source 24A that supplies power to the

magnetron sputtering electrodes

21A and 21B. 24B and transformers 23A and 23B as power control means.

As shown in FIG. 1, film

formation process regions

26A and 26B are formed on the front surfaces of the

sputtering sources

20A and 20B, respectively. The film forming

process regions

26A and 26B are surrounded on four sides by a partition wall 13 protruding from the inner wall surface of the vacuum vessel 11 toward the rotary drum 12, so that each can secure an independent space inside the vacuum vessel 11. It is divided into.
The film forming

process regions

26A and 26B are provided with piping so that the sputtering gas stored in the

gas cylinders

25A and 25B can be supplied.

The plasma source 30 is a means for reacting a thin film formed on the substrate S by the

sputtering sources

20A and 20B with a reactive gas to form a compound thin film, which is a known plasma source and is a side wall of the thin film forming chamber 11A. Is provided.
The plasma source 30 includes a case body 31 fixed so as to close an opening formed in the wall surface of the vacuum vessel 11, and a dielectric plate 32 fixed to the case body 31. An area surrounded by the body plate 32 constitutes an antenna housing chamber configured to be evacuated by a vacuum pump. An antenna (not shown) is disposed in the antenna housing chamber, and this antenna is connected to the high frequency power source 34 via the matching box 33 and receives an electric power from the high frequency power source 34 to generate an induction electric field in the reaction process region 36. To generate plasma.
As shown in FIG. 1, reaction process regions 36 are respectively formed on the front surface of the plasma source 30. The reaction process region 36 is surrounded on all sides by a partition wall 14 projecting from the inner wall surface of the vacuum vessel 11 toward the rotary drum 12, and each is partitioned so as to ensure an independent space inside the vacuum vessel 11. ing.
The reaction process region 36 is provided with a pipe so that the reactive gas stored in the gas cylinder 35 can be supplied.

(Film thickness meter 40)
As shown in FIG. 1, the film thickness meter 40 of this embodiment is attached to the sputtering apparatus 1.
As shown in FIGS. 2 and 3, the film thickness meter 40 includes a light source 41, an optical fiber 42, a light projecting photometric probe 43, a light projecting side lens 51, a light receiving side lens 52, and a light receiving photometric probe 44. An optical fiber 45, an optical detection device 46, an integration amplifier 48 for converting the received light signal detected by the optical detection device 47 into a light amount signal, and receiving the light amount signal from the integration amplifier 48 to perform film thickness control and the like. A control device 47 is provided as a main component.
The light source 41 is a device that emits white light by power supplied from a power source (not shown), and a known halogen lamp is used in this embodiment.

One end of a known optical fiber 42 is connected to the light source 41, and a light projecting photometric probe 43 is provided at the other end of the optical fiber 42. The light projecting photometric probe 43 has a structure in which the end of the optical fiber 42 is housed inside a cylindrical member, and the side wall of the vacuum container 11 is substantially perpendicular to the side surface of the rotary drum 12. The photometering window 17 fitted in this hole is disposed outside the side wall of the vacuum vessel 11 with its end facing the photometric window 17.

A light projecting side lens 51 is disposed between the rotary drum 12 and the light projecting photometric probe 43. The light projecting side lens 51 has a diameter of 10 to 20 mm and is a known achromatic lens used for an optical film thickness meter. The light projecting side lens 51 is irradiated from the light projecting photometric probe 43 and converges the light spreading in a wide angle to irradiate the substrate S.
The light projecting photometric probe 43 is disposed in the vicinity of the focal point of the light projecting side lens 51.
A light receiving side lens 52 is disposed between the rotary drum 12 and the light receiving photometric probe 44. The light-receiving side lens 52 has a diameter of 15 to 30 mm and is made of a known achromatic lens used in a general optical film thickness meter. The light-receiving side lens 52 converges the reflected light from the substrate S spreading over a wide angle and irradiates the photometric probe 44 for light reception.
An achromatic lens is an achromatic lens in which chromatic aberration is corrected at two wavelengths, and is realized by combining two or more lenses. The achromatic lens corresponds to the grouped lens in the claims.

The light projecting side lens 51 and the light receiving side lens 52 are arranged in parallel on the optical paths of the measurement light and the reflected light, as shown in FIGS.
The center 51C of the light projecting side lens 51 and the center 52C of the light receiving side lens 52 have substantially the same distance from the substrate S.
An angle α between the optical axis 51a of the light projecting side lens 51 and the optical axis 52a of the light receiving side lens 52 is 3 to 10 °.

A bisector B that bisects the angle between the optical axis 51a and the optical axis 52a passes through the substrate S and has a larger diameter among the light-receiving side lens 52 and the light-projecting side lens 51 provided adjacent to each other. It penetrates the light receiving side lens 52.
That is, the large-diameter light receiving side lens 52 is arranged so as to protrude from the bisector B toward the light projecting side lens 51. Accordingly, the film thickness meter 40 can be configured compactly by making the light-projecting lens 51 and the light-receiving lens 52 the angle between the

optical axes

51a and 52a as small as 3 to 10 °. The effective diameters of the light projecting side lens 51 and the light receiving side lens 52 can be secured sufficiently large, and a more accurate film thickness meter can be obtained. In addition, the effective diameter of the light receiving side lens 52 can be made sufficiently large, and even when the angle of the substrate is inclined with respect to the optical axis of the light projecting side lens 51, it is possible to make it difficult to come off from the light receiving lens 52. .
At this time, the distance WD between the light projecting side lens 51 and the light receiving side lens 52 and the substrate S is 75 to 350 mm. The distance S1 between the light projecting side lens 51 and the light projecting photometric probe 43 and between the light receiving side lens 52 and the light receiving photometric probe 44 is 35 to 90 mm, and WD is larger than S1.
By doing so, the light incident on the substrate becomes closer to parallel light, and the film thickness can be measured with higher accuracy.

The light-receiving photometric probe 44 is made of a cylindrical member and receives the reflected light guided from the light-receiving side lens 52.
The light-receiving photometric probe 44 is disposed in the vicinity of the focal point of the light-receiving side lens 52.
In the present embodiment, since the focal lengths of the light projecting side lens 51 and the light receiving side lens 52 are substantially the same, the light receiving photometric probe 44 is aligned with the light projecting photometric probe 43 on the side surface of the rotary drum 12. It is disposed outside the side wall of the vacuum vessel 11 with its end facing the photometric window 17 fitted in the hole on the side wall of the vacuum vessel 11 so as to face each other.
As shown in FIG. 2, one end of the optical fiber 45 is housed in one end of the light-receiving photometric probe 44, and the other tip is connected to the optical detection device 46.
The optical detection device 46 is a known collimator made of a flat plate member having a thin slit, deflects reflected light, known grating for emitting only light of a predetermined wavelength out of light incident from the collimator, and grating It is a well-known optical detection device provided with a photodiode for detecting light emitted from.
The optical detection device 46 is connected to a control device 48 via an integration amplifier 47, and is configured such that the control device 48 can control the film thickness based on a light reception signal detected by the optical detection device 46.

Next, operation | movement of the film thickness meter 40 of this embodiment is demonstrated.
First, in each of the

sputtering sources

20A and 20B, the pair of

targets

22A and 22B are held by the pair of

magnetron sputtering electrodes

21A and 21B. The thin film forming chamber 11A is brought into a vacuum state of about 10 ⁻² Pa to 10 Pa by evacuating by operating the vacuum pump.

Thereafter, the substrate S is attached to the rotary drum 12 with the rotary drum 12 locked at the position of the load lock chamber 11B. Next, the load pump chamber 11B is evacuated by operating the vacuum pump, and a vacuum state of about 10 ⁻² Pa to 10 Pa is set. Next, the door between the thin film forming chamber 11A and the load lock chamber 11B is opened, the rotating drum 12 is moved to the thin film forming chamber 11A, and the door is closed again. The inside of the vacuum vessel 11 and the inside of the antenna housing chamber are depressurized to a predetermined pressure.
Thereafter, after the pressure inside the vacuum vessel 11 and the inside of the antenna housing chamber is stabilized, the pressure in the film forming process region 26A is adjusted to 1.0 × 10 ⁻¹ Pa to 1.3 Pa.

Next, the rotating drum 12 is rotated by operating a motor (not shown).
When the rotational speed of the rotary drum 12 becomes substantially constant, the operator turns on a switch (not shown) of the light source 41 and starts projecting continuous light from the light source 41. Light from the light source 41 is transmitted through the optical fiber 42 and irradiated onto the surface of the substrate S from the end of the light projecting photometric probe 43.

Next, thin film formation processing is started in the film forming process area 26A and the reaction process area 36. In the film forming process region 26A, sputtering is performed on the pair of targets 22A, and a thin film made of metal or an incomplete reaction product of metal is formed on the surface of the substrate S. In the subsequent reaction process region 36, an intermediate thin film mainly composed of a complete reaction product of metal is formed by introducing a reactive gas into the thin film formed in the film formation process region 26A.

The current address of the rotary drum 12 is detected by the timing sensor 16, and the control device 48 determines whether it is an address at which sampling of light amount data is started. When the current address is an address at which light quantity sampling is started, a sampling start signal is transmitted from the control device 48 to the optical detection device 46, and light quantity data sampling is started.

When the measurement light is continuously irradiated from the light source 41 to the surface of the rotary drum 12 and the substrate S held by the rotary drum 12, the light is projected when reaching the address at which sampling of the light amount data is started. The measurement light projected from the light metering probe 43 and converged by the light projecting side lens 51 irradiates the substrate S.
The measurement light is reflected by the substrate S, and the reflected light is received and converged by the light receiving side lens 52 and received by the optical detection device 46 from the light receiving photometric probe 44 through the optical fiber 45. The optical detection device 46 detects the intensity of the received reflected light and transmits a received light signal to the integrating amplifier 47. The integrating amplifier 47 converts this received light signal into a light amount signal and transmits it to the control device 48.

Next, the control device 48 determines whether or not the current address detected by the timing sensor 16 is an address at which sampling of the light amount data is finished. If the current address is an address at which the sampling of the light amount data is finished, the sampling of the light amount data is ended.
Thereafter, the control device 48 calculates the light amount by integrating the intensity of the light received between the address where the sampling of the light amount data is started and the address where the sampling is finished, and based on this light amount, the film thickness is determined by a known method. Perform the operation.
The sampling of the light amount data and the film thickness calculation based on the light amount are performed until the obtained film thickness data matches the desired film thickness value set first.

When the film thickness data matches the desired film thickness value, the thin film forming process in the film forming process region 26A and the reaction process region 36 is terminated by a command from the control device 48.
Next, thin film formation processing is started in the film formation process region 26B and the reaction process region 36. In this process, the thin film forming process in the film forming process area 26A and the reaction process area 36, the same process as the sampling of the light amount data, and the film thickness calculation are performed, and when the film thickness data matches the desired film thickness value. Then, the thin film forming process in the film forming process region 26B and the reaction process region 36 is terminated by a command from the control device 48.

In the present embodiment, the light projecting side lens 51 and the light receiving side lens 52 are configured as separate lenses, but instead of the light projecting side lens 51 and the light receiving side lens 52, as shown in FIG. The lens and the light-receiving side lens may be used together, and the lens may be configured as an integral light-receiving / light-receiving side lens 53 that guides both the measurement light applied to the substrate S and the reflected light from the substrate S. At this time, the measurement light and the reflected light can be separated by providing a beam splitter 54 that transmits the measurement light and reflects the reflected light on the opposite side of the substrate S of the light emitting / receiving lens 53.
The light emitting / receiving lens 53 has a diameter of 15 to 40 mm and is a known achromatic lens used in a general optical film thickness meter. The achromatic lens corresponds to the grouped lens in the claims.
The beam splitter 54 shown in FIG. 4 is composed of a known plate beam splitter, but measures a beam branch plane that transmits measurement light incident from the opposite side of the substrate S and reflects reflected light incident from the substrate S side. It suffices if it is provided at an angle of 45 ° with respect to the optical axis of the light and the optical axis of the reflected light, and it may be composed of a cube beam splitter and a pellicle beam splitter.

In addition, an aperture member 55 is provided between the beam splitter 54 and the light projecting photometric probe 43, and the aperture member 55 has an aperture 55a for shaping the shape of the light beam emitted from the light projecting photometric probe 43. Is formed. The aperture 55a has a shape that can limit the amount of light projected at a position corresponding to the optical path of the reflected light from the substrate S by about 20 to 50%.

As described above, since the aperture 55a is provided, even if the substrate S is slightly inclined with respect to the plane perpendicular to the optical axis of the measurement light and the incident angle of the measurement light is changed, the reflected light is rotated. Spreading along the rotation direction V of the drum 12 is suppressed. As a result, it is possible to suppress the reflected light from protruding from the light projecting / receiving lens 53, and to suppress an error in the film thickness measurement value due to variations in the substrate angle.
Instead of providing the aperture member 55, a silver film in which a hole having a shape capable of limiting the amount of light projected at a position corresponding to the optical path of the reflected light from the substrate S by about 20 to 50% is formed in the beam splitter 54. A reflective metal such as may be attached.

In the example of FIG. 4, the distance WD between the light projecting / receiving side lens 53 and the substrate S is 75 to 350 mm, and the distance S2 between the light projecting / receiving side lens 53 and the light projecting photometric probe 43 is 35 to 35 mm. 90 mm.
Thus, by configuring the WD to be longer than S2, the measurement light incident on the substrate S can be made to be close to parallel light.
The light-receiving photometric probe 44 is positioned closer to the substrate S than the light-projecting photometric probe 43 and the beam splitter 54, and to the position on the opposite side of the light-projecting photometric probe 43 with respect to the optical axis of the light-projecting / receiving-side lens 53. The light projecting photometric probe 43 is installed at an angle.

In the example in which the beam splitter 54 and the aperture member 55 in FIG. 4 are provided, the measurement light irradiated from the light projecting photometric probe 43 is projected by the aperture 55a at a position corresponding to the optical path of the reflected light from the substrate S. After the amount of light is limited by about 20 to 50%, the light is transmitted through the beam splitter 54, guided by the light projecting / receiving side lens 53, and irradiated onto the substrate S. A part of the measurement light incident on the substrate S is reflected by the substrate S, guided by the light projecting / receiving lens 53 and incident on the beam splitter 54. The reflected light is reflected in the vertical direction by the beam splitter 54 and received by the photometric probe 44 for light reception.
In the example of FIG. 4, the aperture member 55, the beam splitter 54, and the light projecting / receiving side combined lens 53 are the light projecting side lens unit, the light projecting / receiving side combined lens 53, and the beam splitter 54 are within the scope of the claims. Corresponds to the light-receiving side lens unit.

Moreover, it is good also as a lens structure as FIG. 5, FIG. 6 instead of the lens structure of FIG. 3, FIG.
In the example of FIGS. 5 and 6, a light projecting side lens 56, a light receiving side lens 57, and a condensing lens 58 are disposed between the light projecting photometric probe 43 and the rotary drum 12.

On the substrate S side of the light projecting side lens 56 and the light receiving side lens 57, there is provided a condensing lens 58 that is used both for guiding the measurement light passing through the light receiving side lens 57 and for guiding reflected light from the substrate S. It has been. The diameter of the condensing lens 58 is 40 mm, which is larger than the sum of the diameters of the light projecting side lens 56 and the light receiving side lens 57.
The condensing lens 58 is disposed so that one surface thereof faces the light projecting side lens 56 and the light receiving side lens 57 and the other surface thereof faces the substrate S.
The distance WD between the condenser lens 58 and the substrate S is 75 to 350 mm, and the distances S3 and S4 between the light receiving side lens 57 and the light receiving photometric probe 44 are 35 to 90 mm.
5 and 6, the light receiving photometric probe 44 and the light projecting side lens 56 are arranged closer to the condenser lens 58 and the substrate S than the light projecting measuring probe 43 and the light receiving side lens 57, respectively. Has been. Therefore, the position where the light receiving measurement probe 44 and the light receiving side lens 57 are sandwiched between the light projecting measuring probe 43 and the light projecting side lens 56 in a direction substantially along the traveling direction of the measurement light and the reflected light. It has become a relationship.
The light projecting side lens 56 is a lens for guiding the measurement light from the light projecting photometric probe 43 and has a diameter of about 15 mm. The light-receiving side lens 57 is a lens that guides reflected light from the substrate S, and has a diameter larger than that of the light-projecting

side lens

56 and 20 mm. Other configurations of the light projecting side lens 56 and the light receiving side lens 57 are the same as those of the light projecting side lens 51 and the light receiving side lens 52, respectively.

The light projecting side lens 56 and the light receiving side lens 57 are arranged such that the center 56C of the light projecting side lens 56 and the center 57C of the light receiving side lens 57 are located on both sides of the optical axis 58a of the condenser lens 58. Yes. As shown in FIGS. 5 and 6, the optical axis 58 a of the condensing lens 58 is the end of the large-diameter light receiving side lens 57 among the light receiving side lens 56 and the light projecting side lens 57 provided adjacent to each other. It is arranged so that the parts are close. Further, the optical axis 58 a of the condenser lens 58 may be disposed so as to penetrate the large-diameter light-receiving side lens 57.
The light projecting photometric probe 43 is disposed in the vicinity of the focal point of the light projecting side lens 56, and the light receiving photometric probe 44 is disposed in the vicinity of the focal point of the light receiving side lens 57. In the example of FIGS. 5 and 6, since the focal length of the light projecting side lens 56 is longer than the focal length of the light receiving side lens 57, the light receiving photometric probe 44 is larger than the light projecting photometric probe 43. Although it arrange | positions at the side, it is not limited to this.

5 and 6, the measurement light projected from the light projecting photometric probe 43 is incident on the condensing lens 58 through the light projecting side lens 56, and converged by the condensing lens 58. S is irradiated. The measurement light is reflected by the substrate S, and the reflected light is guided to the condenser lens 58. The guided measurement light is converged by the light receiving side lens 57 and received by the light receiving photometric probe 44.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.
(Simulation example 1: Relative reflectance)
A sputtering apparatus 1 in which a substrate S having an effective measurement range of 20 mm in diameter is mounted on a rotary drum 12 having a diameter of 500 mm, a film thickness meter according to Example 1 having the lens arrangement shown in FIG. 3, and the arrangement shown in FIG. A simulation was conducted in the case where the film thickness meter according to Example 2 and the film thickness meter according to Comparative Example 1 were installed.
Here, the lens arrangement of the proportional 1 is such that a single condensing lens (not shown) is placed between the substrate S and the light projecting photometric probe 43 and the light receiving photometric probe 44 as an axis of the light projecting photometric probe 43. On the other hand, the lens arrangement of the prior art provided substantially perpendicularly is used.
The distance WD between the condensing lens (not shown) of FIG. 3 and FIG.

The substrate S held on the rotary drum 12 is inclined at each angle within a range of 0.0 ° to 2.0 ° with respect to the surface facing the light projecting photometric probe 43 and the light receiving photometric probe 44. Was arranged.
That is, in the case of Example 1 in FIG. 3, 0.0 ° to 2.0 ° with respect to the plane perpendicular to the bisector B that bisects the angle between the optical axis 51a and the optical axis 52a. The arrangement was inclined at each angle within the range of.
Further, in the case of Example 2 and Comparative Example 1 in FIG. 4, 0.0 ° to 2.0 ° with respect to a plane perpendicular to the optical axis of the light emitting / receiving lens 53 or a condensing lens (not shown). The arrangement was inclined at each angle within the range of.
In this state, the relative reflectance was calculated.
The relative reflectance was calculated by calculating the intensity of light projected from the light source and received by the optical detection device 46. For each of Examples 1 and 2 and Comparative Example 1, the relative reflectance at each tilt angle was calculated using the calculated value when the tilt angle of the substrate S was 0.0 ° as a standard value.
Table 1 and FIG. 7 show the calculation results of the relative reflectance (%) at each inclination angle of Examples 1 and 2 and Comparative Example 1.

As shown in Table 1, when the inclination of the substrate S is 1.2 °, the relative reflectance is 68.9% and the rate of change in the amount of reflected light is about 31%. That is, when the substrate S having an effective measurement range of 20 mm is mounted on the rotary drum 12 having a diameter of 500 mm, the substrate is measured during film thickness measurement due to uneven rotation of the rotary drum 12 or mounting errors of the substrate S to the rotary drum 12. Although S can be tilted up to about 1.2 °, in contrast 1, the amount of reflected light is reduced by about 30% due to the tilt of the substrate S that can generally occur as an error. As a total, it was found that there was no practical degree of accuracy.

On the other hand, in Examples 1 and 2, the relative reflectance when the inclination of the substrate S is 1.2 ° is 90% or more, and the substrate S has an inclination that can generally occur as an error. Moreover, the rate of change in the amount of reflected light was only 5.8% and 0.4%, respectively.
In general, when a film thickness is measured with an optical film thickness meter in a rotary thin film forming apparatus, due to a mounting error or rotation unevenness of the substrate S, depending on the diameter of the rotating drum and the size of the substrate S, Inclination varies by several degrees, but according to the film thickness meters of Examples 1 and 2, even when the substrate S is tilted by several degrees, a practically sufficient amount of reflected light can be obtained, which is accurate as a film thickness meter. It was found that sex was secured.

(Experimental example 1)
The film thickness is controlled by the film thickness meter 40 having the lens arrangement shown in FIG. 3 and the experiment for forming the multilayer AR film on the substrate S is repeated a plurality of times, and the light amount change during the thin film formation and the multilayer AR film The variation of spectral characteristics was examined. At this time, the distance WD in FIG. 3 was 200 mm, and the diameters of the light projecting side lens 51 and the light receiving side lens 52 in FIG. 3 were 30 mm and 20 mm.

In this example, silicon (Si) is used as the first target 22A, niobium (Nb) is used as the second target 22B, and the sputtering gas introduced into the film forming

process regions

26A and 26B in the sputtering apparatus 1 of FIG. Argon gas is used as a reactive gas introduced into the reaction process region 36, and silicon oxide (SiO ₂ ) and niobium oxide (Nb ₂ O) are formed on the plurality of substrates S held on the rotary drum 12. ₅ ) An optical multilayer film in which three thin films are alternately laminated, that is, a thin film of SiO ₂ —Nb ₂ O ₅ —SiO ₂ —Nb ₂ O ₅ —SiO ₂ is laminated in the order closer to the substrate S. A multilayer film having a five-layer structure was formed.

At this time, the film thickness of the first SiO ₂ layer and the second Nb ₂ O ₅ layer was controlled by an absolute value control method. That is, using the film thickness meter 40 arranged in FIG. 3, the measurement light emitted from the light source 41 is irradiated from the light projecting photometric probe 43 toward the substrate S, and the reflected light received by the light receiving photometric probe 44 is reflected. The film thickness is monitored by detecting the intensity with the optical detection device 46, calculating the amount of light with the control device 48 based on the intensity data of the reflected light, and monitoring the fluctuation state of the light amount change curve in which the amount of light is plotted. did. The film formation was terminated when the film thickness reached a predetermined target value.
Further, at the end of the second layer film formation, the film formation rate coefficient for time control was calculated by dividing the film thickness when the film formation was completed by the film formation time required for the film formation.

Further, the film thickness of the third SiO ₂ layer was controlled by the B / A control method using the film thickness meter 40 having the lens arrangement shown in FIG.
The B / A control method is to irradiate the generated thin film with monitor light, measure the change in transmittance of the monitor light transmitted / reflected from the thin film, and to express a certain amplitude, maximum value, This is a method of controlling a trajectory having a minimum value by using a ratio (B / A) of a change A from an extreme value of the stop light amount B with respect to an upper and lower width A of the trajectory. In this example, when the B / A value based on the actual transmittance change coincides with the B / A value corresponding to the desired film thickness, the film formation is stopped, so that the film thickness during the film formation can be reduced. Set to thickness.
At the end of the third layer film formation, the film formation rate coefficient for time control was calculated by dividing the film thickness at the end of film formation by the film formation time taken for film formation.

The film thicknesses of the fourth Nb ₂ O ₅ layer and the fifth SiO ₂ layer were controlled by a time control method using the film formation rate coefficients calculated during the formation of the second and third layers. In other words, the film formation times of the fourth layer and the fifth layer are calculated from the film formation rates of the second layer and the third layer and the desired film thicknesses formed by the fourth layer and the fifth layer, respectively. The fourth layer and the fifth layer were formed by performing this step for forming the film.

The film formation process of the multilayer film having the five-layer structure was repeated three times to obtain Samples 1 to 3 having the five-layer AR film on the substrate S. FIG. 8 shows a graph of the change in light amount during film formation of samples 1 to 3. As shown in FIG. 8, in the three samples in which the same process was repeated, almost the same change in the amount of light was shown, indicating that the reproducibility was high.
FIG. 9 shows a graph of spectral characteristics of Samples 1 to 3 having a 5-layer AR film on the substrate S. As shown in FIG. 9, Samples 1 to 3 have almost the same spectral characteristics, and by controlling the film thickness using the film thickness meter of this example, a five-layer AR having substantially the same spectral characteristics. It was found that the film can be formed with good reproducibility.

B Bisecting line S Substrate Z Rotating shaft 1 Sputtering device 11 Vacuum vessel 11A Thin film forming chamber 11B Load lock chamber 12

Rotating drums

13 and 14 Partition wall 15 Timing detecting reflector 16 Timing sensor 17 Measuring

windows

20A and

20B Sputtering source

21A, 21B

Magnetron sputtering electrodes

22A, 22B Targets 23A,

23B Transformers

24A, 24B

AC power supplies

25A,

25B Gas cylinders

26A, 26B Deposition process area 30 Plasma source 31 Case body 32 Dielectric plate 33 Matching box 34 High frequency power supply 35 Gas cylinder 36 Reaction Process area 40 Film thickness meter 41 Light source 42 Optical fiber 43 Light metering probe 44 Light metering probe 45 Light fiber 46 Optical detector 47 Integrating amplifier 48

Controllers

51, 56 Lenses 51C, 52C, 5 on the light emitting side C,

57C center

52 and 57 receiving side lens 53 projecting the light receiving side combinational lens 54 the beam splitter 55 aperture member 55a aperture 58 converging lens

Claims

A reflective optical film thickness meter that is attached to a substrate holder of a rotary optical thin film forming apparatus and measures the film thickness of an optical thin film on a substrate that is rotating according to the rotation of the substrate holder,
A light projecting unit that projects measurement light toward the rotating substrate;
A light-projecting side lens unit comprising a light-projecting lens that is disposed between the light projecting unit and the substrate, receives the measurement light emitted from the light projecting unit, and guides the measurement light to the substrate. When,
A light receiving unit for receiving reflected light of the measurement light from the substrate;
A light-receiving-side lens unit that is disposed between the light-receiving unit and the substrate, includes a light-receiving-side lens that receives reflected light from the substrate and guides the reflected light to the light-receiving unit,
The light path of the light receiving side lens unit and the light path of the light projecting side lens unit are at least partially separated,
An optical film thickness meter, wherein an effective area of the light-projecting lens unit is smaller than an effective area of the light-receiving lens unit.
The light-projecting side lens and the light-receiving side lens are separate and independent lenses,
2. The optical film thickness meter according to claim 1, wherein an effective diameter of the lens on the light emitting side is smaller than an effective diameter of the lens on the light receiving side.
The angle between the optical axis of the light-projecting lens and the optical axis of the light-receiving lens is 3 ° or more and 10 ° or less,
The distance from the lens on the light projecting side to the substrate is longer than the distance from the light projecting unit to the lens on the light projecting side,
3. The optical film thickness meter according to claim 2, wherein a distance from the light receiving side lens to the substrate is longer than a distance from the light receiving unit to the light receiving side lens.
The angle formed between the optical axis of the light-projecting lens and the optical axis of the light-receiving lens passes through the intersection of the optical axis of the light-projecting lens and the optical axis of the light-receiving lens. 4. The optical film thickness meter according to claim 2, wherein the lens on the light receiving side is disposed at a position where the straight line passes.
Between the light-projecting side lens and the light-receiving side lens and the measurement target substrate, the light-projecting side lens, the light-receiving side lens, and a condensing lens facing the substrate,
5. The optical film thickness meter according to claim 1, wherein an effective diameter of the condenser lens is larger than a sum of an effective diameter of the light-projecting lens and an effective diameter of the light-receiving lens. .
The light projecting side lens and the light receiving side lens are composed of a single lens for both light projecting and receiving side formed integrally,
A beam splitter having a beam branching surface that transmits the measurement light and reflects the reflected light at the same time and is inclined with respect to the axis of the reflected light is disposed between the lens for light emitting and receiving side and the light receiving unit. The optical film thickness meter according to claim 1, wherein:
An aperture for limiting the amount of measurement light emitted from the light projecting unit is provided between the light projecting / receiving lens and the light projecting unit,
The optical film thickness meter according to claim 6, wherein the light projecting side lens unit includes the light projecting / receiving side lens, the beam splitter, and the aperture.
The optical film thickness meter according to any one of claims 1 to 7, wherein the lens is composed of a combined lens in which a plurality of lenses are combined so as to remove aberration of a beam of light emitted from the lens.
A substrate holder that can rotate while supporting the substrate in a vacuum vessel;
A thin film forming means disposed to face the substrate held by the substrate holder;
An optical film thickness meter that measures the film thickness of the optical thin film on the substrate by irradiating the substrate with measurement light while the substrate holder to which the substrate is attached is rotating. A device,
The optical film thickness meter comprises the optical film thickness meter according to any one of claims 1 to 8.
A reflective film thickness measuring method for measuring the film thickness of an optical thin film formed on a rotating substrate according to the rotation of a substrate holder of a rotary optical thin film forming apparatus,
The measurement light is projected from the light projecting unit through the light projecting side lens unit including the lens on the light projecting side toward the rotating substrate,
The reflected light of the measurement light reflected by the substrate is provided with a light receiving side lens, and has an optical path at least partially separated from the light path of the light projecting side lens unit. The light is guided to the light receiving unit through the light receiving side lens unit having an effective area larger than the effective area,
A film thickness measuring method comprising measuring the film thickness of the optical thin film by analyzing light quantity data of the reflected light received by the light receiving section.